1. Field of the Invention
The current invention relates to digital image enhancement, and in particular to a method of enhancing the brightness and the contrast of a digital image.
2. Background Information
Digital images, either still or video, are not always captured under ideal lighting conditions. Natural lighting conditions can often be too bright or too dim and artificial lighting outside of a photographic studio often provides irregular illumination. This results in the captured image having poor visual quality. In addition modern the range of luminance in the real world is continuous in both brightness and time and can reach up to 14 orders of magnitude (10 to the power 14). The human eye can see a wide luminance range of up to 5 orders of magnitude, however most display image system only operate at 2 to 3 orders of magnitude.
Various techniques have been proposed in the art for improving or enhancing image quality. More recent methods of enhancing an image are disclosed in US patent publications US 2008/0101719 to Lim et al, US 2008/0012992 and 2007/0171310 to Arici et al and US 2007/0071350 to Lee et al. US publication 2008/0101719 to Lim, in particular, gives a good discussion on the various well known techniques for improving image quality. All of these various methods are successful in improving image quality to varying degrees. However, there is still a difference between digital images and the actual scene viewed by the human eye.